1. Field of the Invention
The invention relates to the field of liquid cryogenic vaporizing equipment and in particular to cryogenic vaporizers utilizing nonfired heat sources.
2. Description of the Prior Art
Historically liquid cryogen vaporizers utilized fired heat sources for vaporizing the cryogenic liquid. A fired heat source is a heat source which uses an open flame or at least a substantially continuous flame in a combustion chamber to create heat which is then utilized by various means to vaporize the cryogenic liquid. The gas is then used in a wide variety of applications ranging from the field of petroleum engineering through aerospace applications.
However, as off-shore petroleum drilling became a more important segment of oil industry, a need arose to insure that all equipment on the oil rig was flame or spark proof to prevent accidental ignition of leaking petroleum gases and fluids. See Zwick et.al., "Fluid Pumpling and Heating System," U.S. Pat. No. 4,197,712.
Therefore, cryogenic vaporizers were developed which drew energy from the air or sea water, or from nonfired heat sources such as internal combustion engines, see Brigham et.al., "Ambient Air Heated Electrically Assisted Cryogen Vaporizer," U.S. Pat. No. 4,519,213.
Although many of these prior art units were very successful in the applications for which they were used, they all suffered from the limitation as to capacity. For example, a pressurized hydraulic loop is included within the system in those nonfired heat sources utilizing internal combustion engines as the heat source. As the quantity of heat which must be produced by the system increases, design and engineering considerations dictate that the pressures and flow rates in the hydraulic loop also increase. However, as the size and pressure ratings of the hydraulic system increases, the cost and complexity of the component parts for such hydraulic system also make a considerable jump. As a result, the cost and engineering problems which with very large high pressure hydraulic systems in nonfired liquid cryogenic vaporizers begins to render the system impractical, or at the very least, uneconomical.
Therefore, what is needed is a design for a nonfired liquid cryogenic vaporizer which can deliver large quantities of heat to the liquid cryogen but can do so in a manner that does not invoke the special engineering problems typically related to high pressure, large flow rate hydraulic systems of the prior art or which result in the very expensive system.